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Highly oriented pyrolytic graphite chemical bonding structure after gallium implantation
T A O Jafer1, H A A Abdelbagi2, A Sulyok3
1Physics Department, University of Pretoria, Hatfield, Pretoria, South Africa.
Scientific Reports
|November 18, 2025
Summary
Gallium ion implantation into highly oriented pyrolytic graphite (HOPG) causes structural changes, with higher ion energy leading to amorphization. This study found HOPG requires significantly higher displacement per atom (dpa) than previously thought for complete amorphization.
Area of Science:
- Materials Science
- Nanotechnology
- Solid State Physics
Background:
- Highly oriented pyrolytic graphite (HOPG) is a model system for studying graphitic materials.
- Understanding ion implantation effects on HOPG is crucial for applications in electronics and coatings.
- Previous studies suggested a low displacement per atom (dpa) threshold for HOPG amorphization.
Purpose of the Study:
- To investigate the structural modifications in HOPG induced by gallium (Ga) ion implantation.
- To determine the influence of ion energy and fluence on defect formation and amorphization.
- To compare experimental results with theoretical dpa calculations for HOPG amorphization.
Main Methods:
- Gallium ions were implanted into HOPG at various energies (10-30 keV) and fluences (2x10^15 to 5x10^16 Ga+/cm^2).
- Raman spectroscopy was used to analyze structural changes, including defect formation and amorphization.
- Displacement per atom (dpa) values were calculated using SRIM (Stopping and Range of Ions in Matter) software.
Main Results:
- Lower energy (10 keV) implantation at high fluence induced defects, evidenced by changes in Raman D and G peaks.
- Higher energy (30 keV) implantation at the same fluence led to complete amorphization, indicated by merged D and G peaks.
- Experimental dpa values for HOPG amorphization significantly exceeded previously reported thresholds ( >35 dpa vs. 0.2-3 dpa).
Conclusions:
- Ion energy is a critical factor in the amorphization process of HOPG.
- The dpa threshold for complete amorphization of HOPG is substantially higher than previously established.
- Further research is needed to accurately quantify the dpa required for HOPG amorphization.
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